Studies show substantial benefit to reduce morbidity and excess mortality for people living with HIV (PLWH) who adhere to antiretroviral therapy (ART), and to lower the probability of forward transmission to sexual partners. Despite efforts to maintain engagement of PLWH along the treatment cascade, it is estimated that only 6-16% of youth and young adults living with HIV (Y/YALWH) maintain suppressed viral load (VL). ART adherence interventions that leverage software on PCs or through the internet capitalize on consistency in delivery of content and long-term cost savings; however, to date the peer-to-peer interactivity that has come to symbolize Web 2.0 remains underutilized in technology-based adherence approaches. Peer-to-peer support is a recommended strategy to improve ART adherence, is widely used by PLWH, and has an evidence-base for in-person approaches - particularly in adult populations. Youth in the US are increasingly accustomed to technology-mediated peer-to-peer interactions, suggesting that intervention approaches that specifically leverage high-use channels of interpersonal communication and support are needed. The ?Thrive with Me? (TWM) intervention is a technology-delivered peer-to-peer social support intervention grounded in the Information, Motivation, and Behavioral Skills (IMB) model. TWM includes peer-to-peer interaction, ART adherence reminders and self-monitoring, mood and substance use self-monitoring, individually-tailored ART and HIV informational content, and gamification components to optimize ART adherence. A pilot study in adult MSM showed that those randomized to the TWM intervention demonstrated improvements across all ART adherence outcomes compared to control participants, with greatest benefits for recent drug-using MSM. As part of the UNC/Emory Center for Innovative Technology (iTech), we propose to test the efficacy of an adapted version of the TWM intervention, called Y-TWM, for Y/YALWH. In this 4-year study, 350 Y/YALWH between the ages of 15-24 with problematic ART adherence at baseline will be randomized to the Y-TWM or a HIV information-only control intervention for a 5-month period. A target of 50% of Y/YALWH participants with self- reported alcohol and/or illicit drug use will be enrolled. VL and validated self-reported ART adherence measures will be collected at baseline, post-intervention, and 3-, and 6-month post-intervention follow up. We hypothesize that participants in the Y-TWM intervention will demonstrate significant improvements in self- reported ART adherence and VL at post-intervention compared to control participants, with greatest improvements among substance-using YLWH. This proposal is innovative for its use of mobile, gaming, and peer interaction components, which can be readily adopted in clinical and community settings with Y/YALWH. The proposal advances HIV continuum of care science for Y/YALWH by providing a rigorous evaluation of a technology-delivered ART adherence intervention for Y/YALWH at elevated risk for therapeutic failure. If the Y- TWM intervention is demonstrated to be effective, it may be quickly scaled up for wide-scale dissemination. !